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Washington: It’s one thing to make an object invisible, like Harry
Potter’s mythical cloak. But scientists have made an entire event
impossible to see. They have invented a time masker.
Think of it as an art heist that takes place before your eyes and
surveillance cameras. You don’t see the thief strolling into the museum,
taking the painting down or walking away, but he did. It’s not just that
the thief is invisible — his whole activity is.
What scientists at Cornell University did was on a much smaller
scale, both in terms of events and time. It happened so quickly that
it’s not even a blink of an eye. Their time cloak lasts an incredibly
tiny fraction of a fraction of a second. They hid an event for 40
trillionths of a second, according to a study appearing in Thursday’s
edition of the journal Nature.
We see events happening as light from them reaches our eyes. Usually
it’s a continuous flow of light. In the new research, however,
scientists were able to interrupt that flow for just an instant.
Other newly created invisibility cloaks fashioned by scientists move
the light beams away in the traditional three dimensions. The Cornell
team alters not where the light flows but how fast it moves, changing in
the dimension of time, not space.
They tinkered with the speed of beams of light in a way that would
make it appear to surveillance cameras or laser security beams that an
event, such as an art heist, isn’t happening.
The scientists created a lens of not just light, but time. Their
method splits light, speeding up one part of light and slowing down
another. It creates a gap and that gap is where an event is masked.
“You kind of create a hole in time where an event takes place,” said
study co-author Alexander Gaeta, director of Cornell’s School of Applied
and Engineering Physics. “You just don’t know that anything ever
happened.”
This is all happening in beams of light that move too fast for the
human eye to see. Using fiber optics, the hole in time is created as
light moves along inside a fiber much thinner than a human hair. The
scientists shoot the beam of light out, and then with other beams, they
create a time lens that splits the light into two different speed beams
that create the effect of invisibility by being too fast or too slow.
It is the first time that scientists have been able to mask an event
in time, a concept only first theorized by Martin McCall, a professor of
theoretical optics at Imperial College in London.
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